1. Field of the Invention
This invention is related generally to milling tools. More particularly, this invention pertains to an apparatus and method for penetrating a tubular body within a wellbore in order to establish a path of fluid communication between inner and outer surfaces of the tubular. In addition, the present invention relates to a milling tool that creates a path of fluid communication from a tubing retrievable subsurface safety valve, to a wireline retrievable subsurface safety valve in order to provide hydraulic pressure to operate the wireline retrievable safety valve.
2. Description of the Related Art
In hydrocarbon producing wells completed with production, there is often a need to cut, punch, drill, mill, dissolve or otherwise remove material in-situ deep in a well. In some cases, cutting the production tubing is desirable. In others, releasing a packer, parting a sleeve, or opening a communication port is the objective. The present invention provides a milling machine that is adapted for use downhole, and may be used in a variety of applications.
A milling machine, in general terms, is a device that has a cutting head rotated against a stationary body. The cutting head includes a blade that cuts against the stationary body, such as a tubular body within a wellbore. Various types of milling machines are known. For example, mill bits are sometimes used in order to cut through a string of casing in order to form a lateral borehole within a wellbore. In such instances, a milling bit is urged downwardly against a diverter tool, such as a whipstock, in order to force the milling bit to grind against the inner surface of the casing. An elongated, elliptical opening, known as a “window,” is thus formed.
A disadvantage to such milling apparatuses is the difficulty in making a cut at a precise location downhole. For example, it is sometimes desirable to penetrate the housing of a tubing-retrievable safety valve in order to create a path of fluid communication from the hydraulic pressure source of the tubing-retrievable safety valve, into the interior bore of the safety valve. This occurs when the tubing-retrievable safety valve has malfunctioned. In such an instance, it is desirable run a second, wireline-retrievable subsurface safety valve (WRSSV) into the wellbore adjacent the defective tubing-retrievable subsurface safety valve (TRSSV), and utilize the hydraulic pressure source of the tubing-retrievable safety valve to operate the wireline-retrievable safety valve. However, there heretofore has been no known mechanical means for accomplishing this milling process.
By way of background, Subsurface Safety Valves (SSVs) are often deployed in hydrocarbon producing wells to shut off production of well fluids in emergency situations. Such SSVs are typically fitted into production tubing in the wellbore, and operate to block the flow of formation fluids upwardly through the production tubing should a failure or hazardous condition occur at the well surface.
The SSV typically employs a valve closure member, or “flapper,” that is moveable between an open position and a closed position. In this respect, the flapper is typically pivotally mounted to a hard seat. When the flapper is in its open position, it is held in a position where it pivots away from the hard seat, thereby opening the bore of the production tubing. However, the flapper is strongly biased to its closed position. When the flapper is closed, it mates with the hard seat and prevents hydrocarbons from traveling up the wellbore to the surface.
The flapper plate of the safety valve is held open during normal production operations. This is done by the application of hydraulic fluid pressure transmitted to an actuating mechanism. A common actuating mechanism is a cylindrical flow tube, which is maintained in a position adjacent the flapper by hydraulic pressure supplied through a control line. The control line resides within the annulus between the production tubing and the well casing, and feeds against a piston. The piston, in turn, acts against the cylindrical flow tube, which in turn moves across the flapper within the valve to hold the flapper open. When a catastrophic event occurs at the surface, hydraulic pressure from the control line is interrupted, causing the cylindrical flow tube to retract, and allowing the flapper of the safety valve to quickly close. When the safety valve closes, it blocks the flow of production fluids up the tubing. Thus, the SSV provides automatic shutoff of production flow in response to well safety conditions that can be sensed and/or indicated at the surface. Examples of such conditions include a fire on an offshore platform, sabotage to the well at the earth surface, a high/low flow line pressure condition, a high/low flow line temperature condition, and simple operator override.
If the safety valve is “slickline retrievable”, it can be easily removed and repaired. However, if the SSV forms a portion of the well tubing, i.e., it is “tubing retrievable”, the production tubing string must be removed from the well to perform any safety valve repairs. Removal and repair of a tubing retrievable safety valve is costly and time consuming. It is usually advantageous to delay the repair of the TRSSV yet still provide the essential task of providing well safety for operations personnel while producing from the well. To accomplish this objective, the tubing-retrievable safety valve is disabled in the open position, or “locked out”. This means that the valve member, i.e., flapper or “flapper plate,” is pivoted and permanently held in the fully opened position.
In normal circumstances, if the well is to be left in production, a WRSSV may be inserted in the well, often in lockable engagement inside the bore within the locked out TRSSV. Because of the insertion relationship, the WRSSV necessarily has a smaller inside diameter than the TRSSV, thereby reducing the hydrocarbon production rate from the well. Locking out the safety valve will not eliminate a need for remediation later, but the lockout and use of the WRSSV will allow the well to stay on production (most often, with a reduced production rate) or perform other work functions in the tubing until the TRSSV can be repaired or replaced.
A novel apparatus and method for locking out a tubing-retrievable safety valve is presented in the pending patent application entitled “Method and Apparatus for Locking Out a Subsurface Safety Valve.” That patent application was filed provisionally on Jul. 12, 2002, and was assigned Ser. No. 60/395,521. A conventional application will be filed under the same title, shortly. That application is incorporated herein fully by reference.
As noted, once a TRSSV is locked out, it is desirable to run in a WRSSV adjacent the TRSSV. In other words, the WRSSV is inserted into the bore of the TRSSV, and then operated in order to provide the safety function of the original TRSSV. This is a more cost-effective alternative to pulling the tubing and attached TRSSV from the wellbore. In order to operate the new WRSSV, a hydraulic fluid source is needed to hold the flapper member of the new WRSSV open. It is preferred to employ the hydraulic flow line already in place for the TRSSV in order to operate the WRSSV. This requires that a communication path be opened between the hydraulic fluid pressure line from the old TRSSV to the new WRSSV.
The present invention is directed to a novel method and apparatus for milling a downhole groove into a tool such as a TRSSV deep in a wellbore. The present inventions are disclosed in the context of creating a path of fluid communication between a TRSSV and a WRSSV disposed therein. However, it is understood that the present inventions are not limited to such use, but that the inventions have many other downhole uses.
Various types of communication devices and methods have been proposed in U.S. Pat. Nos. 3,799,258; 4,944,351; 4,981,177; 5,496,044; 5,598,864; 5,799,949; and 6,352,118. In some of these patents, various additional parts are necessary to enable communication. Where such parts are integral to each and every valve, cost and complexity are obviously added to the valve assemblies. Moreover, modern SSVs are extraordinarily reliable, and such integral communication mechanisms are not used except in a fraction of the total valve population; nevertheless, integral communication mechanisms are included, and add unnecessary cost to most prior art SSV assemblies. Further, integral communication mechanisms may themselves fail to work for various reasons, primarily because the communication mechanisms reside with the SSV's in the harsh downhole environment. Adverse forces include high temperature, high flow rate, sand, corrosion, scale and asphaltine buildup. The forces can cause a failure of the communication mechanism to provide the needed fluid passageway through the TRSSV, and add large and unexpected workover costs.
Other inventors have realized the disadvantages of integral communication mechanisms, and inventions have been disclosed in the US patents discussed below. The trend in these inventions points to a need to remove integral communication mechanisms and requisite structure from the SSV, but none, until the present invention, accomplishes this objective in a reliable, precise, mechanical way.
U.S. Pat. No. 3,799,258 (Tausch '258) discloses a subsurface well safety valve for connection directly to a well tubing for shutting off flow of well fluids through the tubing when adverse well conditions occur. This patent discloses a TRSSV that includes a means for supporting a WRSSV in the event that the first safety valve becomes inoperative. Tausch '258 is instructive wherein the insertable relationship between the TRSSV and the WRSSV is clearly depicted. Tausch '258 provides a fluid control line extending from the surface to a first safety valve. The first safety valve includes a port communicating with the control line and having a shearable device. The shearable device initially closes the port; however, when sheared, it opens the port to allow fluid communication between the hydraulic flow line and the inner bore of the first safety valve. From there, fluid communicates with and controls a second safety valve supported in the first valve bore. A disadvantage to the arrangement of Tausch '258 is that the shearable means can be accidentally sheared during slickline operations, causing hydraulic pressure loss and a malfunction of the first safety valve, i.e., a TRSSV. Further, the device requires a moving sleeve that can become stuck and fail after years of residence in an oil or gas well. Finally, the moving sleeve adds cost to each and every well, whether or not the primary SSV ever fails.
U.S. Pat. No. 4,981,177 (Carmody '177) provides a device integral to a downhole tool, such as a safety valve or a stand-alone nipple. The device has a tubular housing with an axially extending bore being provided along the housing. A radially extending recess is provided in the internal bore wall of the housing, encompassing the axially extending bore. A control fluid pipe is passed through the bore and the recess. A cutting tool is mounted for radial movements in the recess and is actuated by downward jarring forces imparted by an auxiliary tool. When the cutting tool is actuated, the control pipe is severed, and the lower severed end portion of the control pipe is concurrently crimped to close such end portion. This device again adds cost to each and every valve in each and every well, whether or not the primary SSV ever fails. Moreover, the device incorporates moving parts that can become stuck and fail after years of residence in an oil or gas well.
U.S. Pat. No. 4,944,351 (Eriksen, et al. '351) provides a similar method and apparatus to Tausch '258 and Carmody '177. This device features an internally projecting integral protuberance in the bore of the original safety valve housing. A connecting fluid conduit is provided between the interior of the protuberance and the existing control fluid passage. A cutting tool is also integral to the TRSSV, and is mounted on an axially shiftable sleeve disposed immediately above the protuberance. The axially shiftable sleeve is manipulated by a slickline tool that is inserted in the bore of the TRSSV. Movement of the sleeve causes the cutting tool to remove the protuberance, and thus establish fluid communication between the control fluid and the internal bore of the TRSSV housing. Continued well control is assured as control fluid pressure supplied through the opening provided by the severed or removed protuberance operates an inserted WRSSV. However, the protuberance can be accidentally sheared or otherwise damaged during slickline operations, causing hydraulic pressure loss and a malfunction of the TRSSV. Further, the device requires a moving sleeve that can become stuck and fail after years of residence in an oil or gas well. The sleeve is provided in every valve whether used or not, and adds cost to the device.
U.S. Pat. No. 5,496,044 (Beall '044) and U.S. Pat. No. 5,799,949 (Beall '949) recognize the need to remove structure from the TRSSV. The devices of Beall '044 and Beall '949 have internal and external metal-to-metal radially interfering seals that provide an annular chamber. Communication with the annular chamber is established by a slickline tool adapted to punch a hole through the wall of the TRSSV and into the annular chamber. The annular chamber is necessary because the slickline punch tool cannot radially orient to a hydraulic piston hole formed in the TRSSV. The hydraulic chamber undesirably adds a potential leak path if the radially interfering metal-to-metal seals leak. This can cause the premature failure of the TRSSV. The existence of the annular chamber also adds an additional thread to the TRSSV, and the cost associated therewith to each and every TRSSV.
U.S. Pat. No. 5,598,864 (Johnston, et al. '864) discloses a subsurface safety valve, i.e., TRSSV, that has a plug inserted within an opening in the valve housing. This opening is in fluid communication with the piston and hydraulic cylinder assembly of the valve. The plug is adapted to be displaced from the opening to lock out the tubing-retrievable safety valve, and to establish secondary hydraulic fluid communication with an interior of the safety valve in order to operate a secondary WRSSV. The WRSSV is deployed in the primary valve (TRSSV) by slickline, and engages a profile in the TRSSV. Downward force to the deployed WRSSV causes a bolt to shear, thereby pulling the plug out of the opening in the TRSSV and establishing communication. This integral arrangement again adds cost to each and every valve in each and every well, whether or not the primary SSV ever fails. Moreover, the device adds parts that can become stuck or fail after months or years of idle residence in an oil or gas well.
Next, U.S. Pat. No. 5,201,817 (Hailey '817) provides an improvement for a downhole cutting tool otherwise used for many years. This device is used to cut through oilfield tubulars, such as tubing string. The Hailey '817 patent mentions the cleanout of debris, cement, mud, and other materials within a tubular. The cutting action of this tool is rather coarse and cannot be carefully controlled so as to not damage the pressure integrity of a SSV or other downhole device.
Finally, U.S. Pat. No, 6,352,118 (Dickson '118) recognizes the positive attributes of having no additional integral SSV parts to enable communication. Dickson '118 describes a tubular apparatus that delivers a dispersed jet of fluid referred to as a “chemical cutter.” The tubular tool is landed within a TRSSV, and the chemical fluid is then directed against the inner wall of the TRSSV. In operation, the chemical acts against the material of the TRSSV in order to form an opening that provides fluid communication from between the hydraulic fluid source for the valve, and the inner bore.
“Chemical cutters” have been used for decades in the oil industry to “cut” tubing, and are indeed a well-known idiom in the oilfield lexicon. However, a more technically accurate definition is “a chemical reaction of an acid and a base to dissolve a portion of a tool.” The method of Dickson '118 relies on placing a strong acid or other reactant in a local area until the base material is dissolved in situ. This dissolution ostensibly gives an operator the desired result of establishing a communication pathway through the TRSSV. The downside of the apparatus of Dickson '118 is the reliability of the dissolution on a variety of common SSV materials, and the uncertainty of containment of the reaction. For example, if the acid dissolves through the pressure containing body of the TRSSV or contacts the flow tubes, the planned workover can no longer be completed. The completion must be removed from the well, creating expenses of potentially millions of dollars. If the value of the remaining hydrocarbons in the reserve do not justify total re-completion of the well, the result could be a complete loss of the well.
In fairness, the Dickson '118 patent mentions alternatives to chemical cutters. These are listed as “a mechanical cutting tool” and an “explosive cutting mechanism.” However, Dickson '118 never discloses or describes any embodiment or means for utilizing either a mechanical cutting tool or an explosive cutting arrangement within a TRSSV. To the knowledge of the inventors herein, such tools have remained unknown.
There is a need, therefore, for a mechanical communication tool that requires no additional integral SSV parts to enable communication. There is a further need for a communication tool that can be deployed by slickline, and mechanically establishes a fluid communication path from the hydraulic chamber of a primary TRSSV to a secondary WRSSV by milling a groove of a controlled depth in a precise location, and can be used to establish communication in any type of safety valve.
A note about the terms “slickline” and “wireline” is in order: Historically, the term “wireline” has been used to describe all tools lowered in a well that hang on a small diameter wire. Developments in the last several years have some tools being lowered in the well on an “electric line”, where the line not only provides hanging support for the tools, but also provides power and/or communication channels for an electrically operated tool. Often these tools are suspended by braided umbilical cables, and in the most current oilfield vernacular, have also come to be known as “wireline” tools.
Most tools lowered in wells today are mechanical in nature, and require no electric power to operate. In the past, these tools were known as “wireline” tools. However, with the advent of electrical tools, the mechanical tools are now commonly referred to as “slickline” tools rather than “wireline” tools.
One embodiment of the present invention is a “slickline tool” because it is deployed with a battery stack and requires no external power for operation. Typically, slickline operations are less complex than wireline. However, it is obvious that the present invention could also be configured to be deployed on an electrically charged “wireline”. Therefore, for purposes of the present application, the term “slickline” includes cables, electrical lines and wirelines of whatever type.